When disasters happen, many terrestrial infrastructures including cell phones and Internet services become less functional. For emergency and disaster recovery systems, there are needs for real time communications to residents, and rescue workers in disaster areas. It is also important for access of surveillances (videos and images) data over the areas. Unmanned Aerial Vehicle (UAVs) will be very useful tools for these peaceful missions. The proposed systems with three real time functions require for peaceful missions:                1. An ad hoc communications network for local residents, operating in commercial cell phone bands, and/or Wifi bands;        2. An ad hoc communications network for rescue works, operating in emergency bands; and 3. Communications from air mobile surveillance platforms for videos and images to a central hub.        
It is possible to perform all three functions in a large UAV. However, each of the functions may be performed and/or supported by a small UAV. In some embodiments, limits on communications payloads on an UAV may be allocated; such as ˜20 Kg in weight, and 200 W power consumptions, and mission flight time of 12 hours at altitudes at least above the “terrestrial weather” initially. It may also be preferred that the UAVs fly above 5 Km in altitudes.
There are four technologies in architectures for emergency services:                a. UAV as communications nodes;        b. Foreground communications networks between users and UAVs;                    For users with hand-held devices            utilizing remote-beam forming network(RBFN) with the ground-based beam forming (GBBF) facility                        c. Background communications networks, (back channels or feeder-links) between ground infrastructures/facilities and UAVs;                    Back-channels or feeder-links between UAVs and GBBF processing centers.                        d. Wavefront multiplexing/de-multiplexing (WF muxing/demuxing);                    Back-channel calibrations on feeder-link transmission for RBFN/GBBF;            Coherent power combining in receivers on signals from different channels on various UAVs;            Secured transmissions with redundancies via UAVs.                        
Multiple smaller UAVs may be “combined” to perform a function, say communicating with local residents when their cell towers become non-functional. We may fast-deploy 4 small UAVs and group them via communications networks to replace the functions of ill functioned local cell towers or base-stations which are damaged due to current emergencies or disasters. The residents may use their existing personal communications devices including their cell phones to communicate to outside worlds via the ad hoc communications network via these small UAVs. In these cases, we may allocate size, weight, and power (SW&P) limits on communications payloads (P/L) on a small UAV; about <5 Kg in weight, and <50 W power consumptions.
The payloads on surveillance platforms will use optical sensors to generate optical images during day time. There are possibilities of using optical illuminators on the UAVs or different UAVs to allow night operations. Infrared sensors may also be used for night visions and imaging.
Microwave sensors can be used for both night and cloudy (or raining) conditions in which optical sensors may not function well. Active monostatic Radars may be deployed by individual UAVs. Polystatic or multi-static Radars can be deployed via a fleet of UAVs.
Multiple UAVs will be coordinated to form a coherent RF receiving system as a passive Radar receiver via GBBF processing and real time knowledge of the positions/orientations of all receiving elements on various UAV platforms. It will take advantage of ground reflections of existing and known RF illuminators such as Naystar satellite from GPS constellations, or satellites from many other GNSS constellations at L-band. It is also possible to use as RF illuminators by taking advantages of ground reflections of high power radiations by many direct broadcasting satellites(DBS), which illuminate “land mass” with high EIRP over 500 MHz instantaneous bandwidths (of known signals) at S, Ku and/or Ka band. The “known signals” are received signals through a direct path or a second path from the same radiating DBS satellite. Furthermore, high power radiations from Ka spot beams of recently deployed satellites on many satellites either in geostationary or non-geostationary orbits, can also be used as RF illuminators.
The terms of UHF, L, S, C, X, Ku, and Ka bands are following the definitions of IEEE US standard repeated in Table-1.
TABLE 1IEEE Designated Frequency BandsTable of IEEE bandBandFrequency rangeOrigin of name1HF band3 to 30 MHzHigh FrequencyVHF band30 to 300 MHzVery High FrequencyUHF band300 to 1000 MHzUltra High FrequencyL band1 to 2 GHzLong waveS band2 to 4 GHzShort waveC band4 to 8 GHzCompromise between S and XX band8 to 12 GHzUsed in WW II for fire control,X for cross (as in crosshair)Ku band12 to 18 GHzKurz-underK band18 to 27 GHzGerman Kurz (short)Ka band27 to 40 GHzKurz-aboveV band40 to 75 GHzW band75 to 110 GHzW follows V in the alphabetmm band110 to 300 GHz
FIG. 1 illustrates a scenario of UAVs in a rescue mission. Three vital tasks are provided by the UAVs;                1. Communications networks deployment for local residents in disaster areas using their existing cell phones:                    UAV (M1) becomes the replacement of the damaged cell towers in a Spoke-and-hub architecture;            Residents can use their own cell phones ask for assistance when needed.                        2. Communications networks deployment for rescue teams with special phones:                    UAV (M2) becomes the rapid deployed cell towers for communications among the rescue team members and their dispatchers;            Using separate emergency frequency bands;            Spoke-and-hub architecture.                        3. Surveillance platforms for visual observations:                    UAV (M3) takes videos on disaster areas and relays them back to the hub instantaneously;            Dedicated high data rate links.                        
All three major tasks will have the same hub which shall have capability to relay the emergency information to the mission authority. Users on the two networks can communicate among themselves through the gateways which are co-located at the same hub, which shall be standard mobile hubs that telecommunications service providers can support.
An example of desired designs of the communications functions in this disclosure is summarized as follows:                In the airborne segment:                    Using 16 elements as array for foreground communications network;            to enable a 4-element subarray with multiple beam capability maintaining links for data rate at 10 Mbps for each subarray;            to enable a sparse array made from 4 subarrays at S/L bands or C-band with multiple beam capability maintaining links for data rate at 10 Mbps per beam;            to design Ku-band feeder links with a bandwidth at 160 MHz.                        In the user segment:                    Regular cell phones for the residents in the serviced community;            Common rescue mission equipment at 4.9 GHz.                        In the ground segment:                    Three Ku band antennas to track three UAVs concurrently individually with data rate at 150 MHz back channel bandwidths in both directions;            GBBF capability with knowledge of evolving array orientations on UAVs.                        